In many applications, it is necessary to distinguish an original article from a copy or counterfeit to validate the original article. An original article that includes an authenticating feature can be validated in many ways. Some methods involve visible (i.e. overt) authenticating features that are disposed on or incorporated into the article, such as a hologram on a credit card, an embossed image or watermark on a bank note, a security foil, a security ribbon, colored threads or colored fibers within a bank note, or a floating and/or sinking image on a passport. While these features are easy to detect with the eye and may not require equipment for authentication, these overt features are easily identified by a would-be forger and/or counterfeiter. As such, in addition to overt features, hidden (i.e. covert) features may be incorporated in original articles. Examples of covert features include invisible fluorescent fibers, chemically sensitive stains, and taggants such as luminescent pigments or fluorescent dyes that are incorporated into the substrate of the article. Covert features may also include physical properties of the original articles to be validated. For example, for metal articles such as coins, authentication may be determined through conductivity measurements. However, due to cost considerations, many coins are now produced with a soft steel core plated with another metal, such as nickel. The soft steel core generally produces a magnetic signal that masks any magnetic signal from the plated metal and, thus, renders authentication through conventional conductivity measurements difficult.
It is generally known to provide taggants on a surface of metal articles to enable authentication of the metal articles. Existing efforts to employ taggants in metal articles of manufacture involve post metal-forming surface deposition of taggants because taggant costs are prohibitive to dispersing the taggants through the entire material volume when only the surface is subject to authentication. Further, article manufacturing techniques may have an unpredictable effect on taggant properties such that post metal-forming surface deposition of the taggants is the only option. However, post metal-forming surface deposition of the taggants results in weakly adhered taggants that easily wear off. Wear is not a concern when determining if a new product is real or counterfeit when purchased from a supplier because authentication is a one-time event. However, repeat authentication over time is a concern for value articles, such as coins, that are subject to significant wear.
Accordingly, it is desirable to provide metal articles and methods of forming metal articles that include taggants that are robustly adhered to the metal articles. Further, there remains an opportunity for methods of authenticating metal articles with the taggants that are robustly adhered to the metal articles. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.